It is well known in the cardiologic field that diagnosing the presence or absence of coronary disease is enhanced by having the patient's heart undergo stress testing to induce a high enough heart rate at which coronary disease may be detected. However, for various reasons, approximately thirty percent (30.0%) of the patient population is unable to tolerate stress testing to produce a heart rate at which acceptable diagnosis of heart disease is possible.
It is known that a most revealing way to determine the presence and extent of coronary-disease (particularly coronary artery disease) is to monitor the ventricular wall motion of the heart operating at higher beat levels. Techniques to produce a sonogram or echocardiogram of ventricular wall motion are known, and usually involve the use of a transthoracic transducer placed on the outside of the patient's chest in vicinity to the heart to visualize heart wall motion.
At present, in addition to the unpopular (and relatively unsafe) technique of a temporary pacing by means of an intravenous pacing wire implanted in contact with the heart (i.e., the i-v pacemaker), the art has developed two general types of diagnostic tests for patients who cannot be adequately stress tested to permit accurate assessment of coronary disease. First, there is the "pill electrode" type of device, as illustrated in U.S. Pat. No. 4,817,611, whereby the patient is induced to swallow a device which may be used to artificially stimulate (i.e., pace) the heart to higher activity. A second technique is to stress the heart pharmacologically, usually by Dipryridamole. In both situations, the stressed heart's activity is then monitored by radionuclide imaging enhaced by thallium doping. The pharmacological technique has the drawback of possible irreversible medicinal side effects. The "pill electrode" is very uncomfortable to the patient, and the echocardiographic imaging modality associated with the pill electrode (i.e., transthoracic echocardiography) is often unsatisfactory.
The present invention solves the inadequacies of the prior art by providing a single transesophageal probe having the capability to both pace the patient's heart and simultaneously produce a higher quality echocardiographic image of the ventricular wall motion of the patient's heart to permit accurate diagnostic assessment of coronary disease revealed by the stress induced on the paced heart.
Physiologically, transesophageal probes are capable of being located much closer to the heart compared to other devices, since the esophagus actually lays against the heart in the vicinity of the left atrium. Because the transducer which is receiving the sonic energy produced by the reflection of the transducer's sonic output (which is reflective of ventricular wall motion of the stressed heart) is in close proximity to the heart, much closer than is possible with transthoracic echocardiography, a much improved echocardiographic image is produced. Similarly, also because of the proximity of the esophagus to the heart, the pacing electrode mounted on the transesophageal probe may be more easily and precisely placed in relation to the atrial chambers of the patient's heart to permit a more controlled, safer electrical pulse to pace the heart to desired stress levels, than is possible with the pill electrode or other techniques including pharmacological techniques to pace the heart.